The density of a substance, i.e. the mass per unit volume (as grams per cubic centimeter) is one of the most important intensive parameters of a material. The density of condensed matter, such as solids and liquids, and the pressure and/or temperature dependency of the density is of paramount importance for many scientific and technical investigations.
A well known method for the determination of density is the so-called hydrostatic density measurement method. This method is an application of the familiar Archimedes' hydrostatic buoyancy principle and involves the measurement of the upward buoyant force exerted on a body immersed in a fluid of less density as that of the immersed body. The hydrostatic method furnishes the most precise and reliable density values, especially in case of solids, and may be performed with an electronic balance comprising a balance beam coupled to a force measuring system, and a pair of hangdown assemblies supported by the opposite ends of the balance beam. The hangdown assemblies may comprise thin suspension wires and sample and compensating weight supports for supporting a solid sample and a compensating weight, respectively. The sample support generally comprises a pair of sample pans suspended one above the other within a measuring chamber which can be filled with the buoyant liquid up to such a level that the lower pan is immersed in the liquid while the upper pan is above the surface of the liquid. A sinker body is substituted for the immersed weighing pan when the density of a liquid sample is to be measured which in this case is used as buoyant liquid.
It is generally quite difficult, to obtain accuracies in the order of the fourth or fifth or higher decimal place with the known densitometers. This applies specifically if the mass of the sample is small, as below 1 gram, and if the density measurements have to be performed at temperatures differing essentially from the normal room temperature (21.degree. C.) or within an extended temperature range. Further, the known densitometers do not allow fast measurements, as it is specifically desired when a functional dependency of the density on the temperature, the concentration, the molecular structure or variation of the structure are to be measured with sufficient accuracy and within a reasonably small period of time.